A wind power generator (hereinafter referred to as “wind turbine”) is a device in which a rotor head equipped with wind-turbine blades rotates upon receiving wind force, and in which a generator driven by, for example, accelerating this rotation with a gear box generates electricity.
The above-described rotor head is attached at an end portion of a nacelle, which is installed on top of a wind turbine tower (hereinafter referred to as “tower”) in a manner that allows yawing, and is supported so as to be rotatable about a substantially horizontal lateral rotation axis.
As a general device configuration, a device for transmitting a mechanical rotational force received from the wind-turbine blades and a power generator are installed inside the nacelle of the wind power generator. Among those, the rotational-force transmitting device is provided with a main bearing and a gear box, and the power generator is provided with a generator, a transformer, an inverter, and a control panel, or is provided with a generator and a control panel.
Such equipment in the nacelle is cooled by using outside air that is sucked in through a nacelle air inlet, performing heat exchange between the outside air and a coolant with individual heat exchangers, which are installed on each piece of equipment serving as a heat source, and supplying the coolant, whose heat has been absorbed by the outside air, to the equipment to be cooled. In this case, the outside air to be sucked into the nacelle is generally subjected to salt removal treatment and dust removal treatment through a filter.
As a conventional example employing heat exchange between the outside air and the coolant, specific examples of each piece of equipment releasing heat are illustrated in FIGS. 4A and 4B. In FIG. 4A, reference sign 1 in the figure designates a wind power generator, 2 designates a tower, 3 designates a nacelle, 4 designates a rotor head, 5 designates wind-turbine blades, 6 designates a nacelle air inlet, and 7 designates an air outlet.
In addition, FIG. 4B is an enlarged view of relevant portions of the wall surface structure of the nacelle 3. The nacelle wall surface of a general nacelle structure has an outside wall structure that is formed by connecting a plurality of separated wall members 3a, which are made of fiber reinforced plastic (hereinafter referred to as “FRP”), and a structure in which flange parts 3b provided inside the nacelle are connected with bolts and nuts 8 is employed.
With such a wind power generator 1, cooling of a main bearing 9 and a gear box 10, which constitute mechanical transmission devices, is achieved by using lubricating oil, which circulates through a lubricating oil circulatory system, as the coolant for heat exchange with the outside air. In this case, heat exchange between the lubricating oil and the outside air is performed in an oil cooler 11, and lubrication and cooling of frictional heat are achieved by supplying the lubricating oil that has been cooled due to the heat absorption with the outside air to rotating parts.
On the other hand, for cooling the electrical apparatuses that are heat releasing sources, for instance, in the case of an inverter control panel 12, antifreeze is used as the coolant for heat exchange with the outside air, and in the case of a generator 13, primary air is used as the coolant for heat exchange with the outside air. In both cases, continuous cooling is achieved by supplying and circulating the antifreeze or the primary air, which have been taken into the outside air, to electrical apparatuses that are heat sources to be cooled. Reference sign 14 in this figure designates a transformer.
The above-described outside air flows into the nacelle 3 through the nacelle air inlet 6 by operating a fan 15. This outside air flows within the nacelle 3 to exchange heat with various types of coolants, and to ventilate and cool the inside of the nacelle, and after that, the outside air flows out through the air outlet 7.
Because the wall members 3a of the nacelle 3 are made of FRP generally having a wall thickness of about 100 mm, the thermal insulance of the FRP becomes dominant. Therefore, the effect of neat input from sunlight can be effectively negligible in many cases.
PTL 1 below discloses a structure having a heat-shield-coating composition, and a film thereof, having high heat-shielding properties for preventing the intrusion of thermal energy by efficiently reflecting thermal energy such as sunlight.
In addition, in PTL 2, it is described that an ultraviolet-reflecting coating is applied to the blade surfaces of a wind turbine for preventing birds from accidentally colliding or coming into contact with the rotating wind-turbine blades.